A exhaust gas cleaning purifier used in an engine of a locomotive, which is arranged between an exhaust pipe of the engine and a silencer connecting to the exhaust pipe, includes a front supply pipe and a back supply pipe configured for supplying secondary air, at least one front catalyst converter for making an oxidation reaction and at least one middle catalyst converter for making an reduction reaction, and at least one back catalyst converter arranged after the silencer and the back supply pipe. The front supply pipe connects with the exhaust terminal of the engine, and the back supply pipe connects with the silencer. The at least one front catalyst converter and the at least one middle catalyst converter are arranged in the silencer and arranged between the front and back supply pipes. A dissipating-heat distance is defined between the front catalyst converter and the middle catalyst converter.